I have a (private) version of Senpai 1.0 that plays Makruk; as I recall the changes were not too hard to make, so hopefully I can port those over easily.

More painful, I guess, but doable. However reusing eval parts would be more difficult with this version, maybe much more. The weights are probably very specific.

And (say) with your own eval, switching to version 2.0 doesn't make much sense.

Oh, I didn't tune the evaluation (apart from a few very specific things), I made it mainly to have a larger variety of opponents (and as a proof-of-concept that just modifying the move generator of a reasonably strong engine to play a different variant doesn't automatically give you a very strong engine without redoing the evaluation).
From what I remember, most of the work was converting from UCI to CECP (there is some de-facto standard for handling variants with UCI now, but there was nothing back then), which was pretty straightforward.